Dispersion compensation is one of the key elements of high speed optical transmission. Dispersion compensation traditionally involves the use of dispersion compensators at various points along an optical signal propagation path typically at amplifier sites to compensate for the dispersion caused by the fiber and elements along the span since the last dispersion compensation. Dispersion compensator modules (DCMs) are rated by the amount of dispersion they compensate and can be fixed in value or variable (tunable). Variable or tunable functioning of dispersion compensation modules is desirable for numerous reasons including the following: simplification of the network design; allowance of the reconfiguration of the network topology, reduction of inventory; reduction of turn-up time in the field and making the network more robust against aging, temperature change, and re-routing. Each of these represents potential cost savings and potential enhancement of network performance.
In the past, in working towards these benefits, most of the prior art has focused on tunable DCM (TDCM) development. All of the potential TDCM designs to date, however, have issues associated with them which are difficult to overcome. For example Virtual Imaged Phase Array approaches have very low yield due to tight optical alignment, Fiber Bragg Grating (FBG) based technologies have group delay ripple problems, and Fabry-Perot filter (F-P) based technology has a small tuning range.
It would be desirable for there to be a variable or tunable dispersion compensation module which mitigates these problems and moreover is compact and reliable.